1. Field of the Invention
The invention relates to a camera shutter provided with a shutter blade for opening and closing a shutter opening provided on a base plate.
2. Description of the Related Art
A conventional camera shutter such as described in, e.g., JP-A 2001-281724 is known (see FIG. 6). An electromagnetic drive shutter described in JP-A 2001-281724 has a driving means for operating a shutter blade but is not provided with a restraining member at a stop position of a driving lever. In other words, the driving lever immediately starts an operation at a closing position or an opening position of the shutter blade when an operating current is conducted to a magnetic drive coil.
However, in the above-mentioned conventional art, since a restraining member made of a magnetic material for attracting and holding a permanent magnet is not provided at a stop position of the driving lever, a shutter driving means immediately starts an operation when an operation signal is output and the movement is likely to become unstable. In other words, the operation is started in a state that stability of the operation cannot be ensured due to a fitting gap or frictional force between each component, thus, a shutter control tends to be unstable.
Meanwhile, there is a method of attracting and holding by direct contact with the restraining member at the stop position of the driving lever, however, strength of the attractive force is likely to vary due to a roughness condition of both contact surfaces to be attracted and held base on the processing and existence of wave on the whole surface, which causes instability in operating performance. In other words, attracting and holding force is strong when the contact surface is fine and the wave is minimal, on the contrary, the attracting and holding force is weak when the contact surface is rough or the wave is present.
Therefore, it is not possible to separate the both contact surfaces unless magnetic force against the attracting and holding force is generated corresponding to the condition of the both contact surfaces. Furthermore, voltage dependency increases due to such a condition, hence, not preferable. That is, the condition of the contact surface significantly affects function and performance of the operative mechanism.